1. Field of Invention
This invention relates generally to an automated drive system adapted to transfer a hoist from which a work load is suspended from one processing stage to the next in a series thereof, and more particularly to a system in which the hoist is caused by an X-linear motor to travel from stage to stage along a horizontal path, and is caused by a Y-linear motor at each stage to travel in a vertical path to lower the work load into that stage for processing therein and to then raise it for transfer to the next stage.
2. Status of Prior Art:
My prior U.S. Pat. No. 4,575,299 discloses an automated drive system for carrying out chemical processing operations sequentially at a series of work processing stages. In this drive system, a work load suspended from a hoist is caused to travel along a raised horizontal path from stage to stage, the hoist at each stage being lowered to enter the work load therein for processing and then raised so that it can then be transferred to the next stage.
The concern of the present invention is with the processing of substrates for producing microelectronic circuits, such as integrated circuit chips. In the processing of these substrates, it is necessary to transfer a work load of such chips sequentially from stage-to-stage in a series thereof.
The problem with existing motorized drive systems for this purpose is that they include rack and pinion mechanisms, drive gears, lead screws and other devices that are subjected to friction. The resultant abrading action on the contacting surfaces gives rise to fine particulate matter which becomes air borne and creates an atmosphere which contaminates the substrates being processed. Or the contaminants may migrate from their sources to contaminate the substrates. Such contamination cannot be tolerated, for it is damaging to the microelectronic circuits to be produced on these substrates.
A drive system in accordance with the invention includes an X-linear motor to cause a hoist from which a work load is suspended to travel from stage to stage along a horizontal path and a Y-linear motor to cause the hoist at each stage to travel in a vertical path to lower the work load into the processing stage and to then raise it for transfer to the next stage. Hence of prior art interest are the following patents.
A. The Negishi U.S. Pat. No. 4,916,340 shows a movement guidance system useable in the manufacture of semiconductor devices in which two linear motors are provided, one driving a movable member in the X-direction, the other in the Y-direction. In the present specification the term X-linear motor refers to a motor which causes a movable member or hoist to travel along a horizontal path, and the term Y-linear motor refers to a motor which causes a movable member to travel in a vertical path. PA1 B. The patent to Hinds discloses a first linear motor to move a shuttle in the X-direction and a second linear motor to move the shuttle in the Y-direction. PA1 C. The Fritz U.S. Pat. No. 5,688,084 discloses a drive system for a machine tool having X and Y-linear motors. PA1 D. The Teramachi U.S. Pat. No. 4,788,477 shows a motor driven X-Y table employing a linear motor. PA1 E. The Toyoda U.S. Pat. No. 3,904,900 shows two pulse-operated linear motors arranged to transfer an object in the X and Y directions. PA1 F. The Ira U.S. Pat. No. 5,808,382 shows a motor drive for a machine tool having a primary linear motor and a secondary linear motor.
In all of the above-identified prior art patents which disclose X and Y-linear motors, each motor is separately supplied with operating power from an external source. In a drive system in accordance with the invention the X-motor is supplied with operating power from an external source whereas the Y-motor which is electromagnetically coupled to the X-motor inductively derives its operating power from the X-motor.
Also of prior art interest is my prior U.S. Pat. No. 4,466,454 which discloses an automatic work transfer system for conveying a basket carrying work through a row of processing stages at a work station in any desired sequence. The basket is lowered into a tank at each stage and oriented therein for processing for a predetermined dwell period, at the conclusion of which the basket is hoisted out of the tank and transferred to the next stage where the procedure is repeated.
The system includes a supporting rail laterally displaced from the row of stages and parallel thereto. Riding on the rail is a robot provided with a pair of vertical shafts supported on an elevator. Cantilevered from the shafts are a pair of arms which extend over the stages, the ends of the arms which extend over the stages, the ends of the arms being pivotally connected to a cross piece. Depending from the center of the cross piece is a rod terminating in a hand adapted to engage the handle of the basket.
Thus when the robot advances on the rail, the hand is then shifted along a horizontal X-axis to a position in general alignment with a selected stage, when the elevator is operated, the hand is raised or lowered with respect to the selected stage along a vertical Y-axis normal to the X-axis; and when the shafts are simultaneously rotated, the hand swings, but without rotation, relative to a Y-axis perpendicular both to the X and Y axis to orient the basket with respect to the stage. Separately controllable X, Y and Z motors are subject to programmed instruction appropriate to the processing to be carried out.